Simple pedotransfer functions to initialize reactive carbon pools of the <scp>RothC</scp> model

Summary Modelling of carbon turnover is a widely used tool to estimate soil carbon stock changes as a response to climate and land‐use change. Carbon turnover models are increasingly used not only at the point scale but also at regional and continental scales, and the R othamsted carbon model ( RothC ) is a widely used model because of its simplicity and easy implementation. For the initialization of the RothC model, knowledge about the carbon pool sizes is essential. Pool size characterization can be either obtained from physical fractionation or equilibrium model runs, but both approaches are time consuming and tedious, especially for larger scale simulations. In our study, a pedotransfer function ( PTF ) for the estimation of all active carbon pools of the RothC model is presented. As independent variables, only total organic carbon ( TOC ) and clay content, which are easily available at most scales, are necessary. For validation of PTFs the resistant plant material ( RPM ) stock estimated from physical fractionation of soil of a wide range of types was predicted with a R 2 of 0.70. In a second step, associated errors induced by the use of PTFs were analysed by using simulation runs for a 100‐year time period. Thereafter, the model was either initialized by the carbon pools extracted from physical fractionation or the PTF . Maximum relative deviations in TOC content were small (&lt;9%) and declined to &lt;4% after 100 years. Further, absolute errors were within the range of measurement error for soil organic carbon. Therefore, we propose that PTFs can be used to initialize the RothC model whenever physical fractionation is not feasible or equilibrium runs are considered too tedious.